What symptom is commonly associated with a medullary thyroid carcinoma leading to increased calcitonin?

Medullary thyroid carcinoma (MTC) is a type of thyroid cancer that arises from parafollicular C cells, which are responsible for producing calcitonin. Increased levels of calcitonin due to MTC can lead to certain clinical features. One notable symptom associated with elevated calcitonin levels is diarrhea.

Calcitonin plays a role in calcium homeostasis and can influence gastrointestinal motility. In patients with MTC, the circulating high levels of calcitonin can lead to gastrointestinal symptoms, including diarrhea, due to its effect on the gastrointestinal tract. This relationship is particularly relevant as MTC often presents with other symptoms of neuroendocrine tumors, and diarrhea can be a prominent feature in this context.

In summary, the symptom commonly associated with medullary thyroid carcinoma due to increased calcitonin is diarrhea. This effect highlights the endocrine functionality of calcitonin beyond its primary role in calcium metabolism.